Excerpt from mashable.com Thanks to a rare, severe geomagnetic storm, the Northern Lights may be visible on Tuesday night in areas far to the south of its typical home in the Arctic. The northern tier of the U.S., from Washington State to Michiga...
Tag: south (page 3 of 9)
| This artist's impression of the interior of Saturn's moon Enceladus shows that interactions between hot water and rock occur at the floor of the subsurface ocean -- the type of environment that might be friendly to life, scientists say. (NASA/JPL-Caltech) |
Excerpt from latimes.com
Scientists say they’ve discovered evidence of a watery ocean with warm spots hiding beneath the surface of Saturn’s icy moon Enceladus. The findings, described in the journal Nature, are the first signs of hydrothermal activity on another world outside of Earth – and raise the chances that Enceladus has the potential to host microbial life.
Scientists have wondered about what lies within Enceladus at least since NASA’s Cassini spacecraft caught the moon spewing salty water vapor out from cracks in its frozen surface. Last year, a study of its gravitational field hinted at a 10-kilometer-thick regional ocean around the south pole lying under an ice crust some 30 to 40 kilometers deep.
Another hint also emerged about a decade ago, when Cassini discovered tiny dust particles escaping Saturn’s system that were nanometer-sized and rich in silicon.
“It’s a peculiar thing to find particles enriched with silicon,” said lead author Hsiang-Wen Hsu, a planetary scientist at the University of Colorado, Boulder. In Saturn’s moons and among its rings, water ice dominates, so these odd particles clearly stood out.
The scientists traced these particles’ origin to Saturn’s E-ring, which lies between the orbits of the moons Mimas and Titan and whose icy particles are known to come from Enceladus. So Hsu and colleagues studied the grains to understand what was going on inside the gas giant’s frigid satellite.
Rather than coming in a range of sizes, these particles were all uniformly tiny – just a few nanometers across. Studying the spectra of these grains, the scientists found that they were made of silicon dioxide, or silica. That’s not common in space, but it’s easily found on Earth because it’s a product of water interacting with rock.
Knowing how silica interacts in given conditions such as temperature, salinity and alkalinity, the scientists could work backward to determine what kind of environment creates these unusual particles.
A scientist could do the same thing with a cup of warm coffee, Hsu said.
“You put in the sugar and as the coffee gets cold, if you know the relation of the solubility of sugar as a function of temperature, you will know how hot your coffee was,” Hsu said. “And applying this to Enceladus’s ocean, we can derive a minimum [temperature] required to form these particles.”
The scientists then ran experiments in the lab to determine how such silica particles came to be. With the particles’ particular makeup and size distribution, they could only have formed under very specific circumstances, the study authors found, determining that the silica particles must have formed in water that had less than 4% salinity and that was slightly alkaline (with a pH of about 8.5 to 10.5) and at temperatures of at least 90 degrees Celsius (roughly 190 degrees Fahrenheit).
The heat was likely being generated in part by tidal forces as Saturn’s gravity kneads its icy moon. (The tidal forces are also probably what open the cracks in its surface that vent the water vapor into space.)
Somewhere inside the icy body, there was hydrothermal activity – salty warm water interacting with rocks. It’s the kind of environment that, on Earth, is very friendly to life.
“It’s kind of obvious, the connection between hydrothermal interactions and finding life,” Hsu said. “These hydrothermal activities will provide the basic activities to sustain life: the water, the energy source and of course the nutrients that water can leach from the rocks.”
Enceladus, Hsu said, is now likely the “second-top object for astrobiology interest” – the first being Jupiter’s icy moon and fellow water-world, Europa.
This activity is in all likelihood going on right now, Hsu said – over time, these tiny grains should glom together into larger and larger particles, and because they haven’t yet, they must have been recently expelled from Enceladus, within the last few months or few years at most.
Gabriel Tobie of the University of Nantes in France, who was not involved in the research, compared the conditions that created these silica particles to a hydrothermal field in the Atlantic Ocean known as Lost City.
“Because it is relatively cold, Lost City has been posited as a potential analogue of hydrothermal systems in active icy moons. The current findings confirm this,” Tobie wrote in a commentary on the paper. “What is more, alkaline hydrothermal vents might have been the birthplace of the first living organisms on the early Earth, and so the discovery of similar environments on Enceladus opens fresh perspectives on the search for life elsewhere in the Solar System.”
However, Hsu pointed out, it’s not enough to have the right conditions for life – they have to have been around for long enough that life would have a fighting chance to emerge.
“The other factor that is also very important is the time.… For Enceladus, we don’t know how long this activity has been or how stable it is,” Hsu said. “And so that’s a big uncertainty here.”
One way to get at this question? Send another mission to Enceladus, Tobie said.
“Cassini will fly through the moon’s plume again later this year,” he wrote, “but only future missions that can undertake improved in situ investigations, and possibly even return samples to Earth, will be able to confirm Enceladus’ astrobiological potential and fully reveal the secrets of its hot springs. ”
GanymedeExcerpt from latimes.comAstronomers have found the most conclusive evidence yet that a large watery ocean lies beneath the surface of Jupiter's moon Ganymede.Scientists have suspected for decades that a subterranean ocean ...
Excerpt from cbsnews.comALT LAKE CITY -- Police responding to a report from a fisherman about an overturned car in an icy Utah river were stunned to discover an 18-month-old girl dangling in a car seat inside, unconscious but alive. The officers also ...
Excerpt from autotrader.com By Josh Sadlier Seems like the only thing automakers want to talk about these days is how their cars suddenly get great fuel economy. Given this relentless chatter, it's tempting to conclude that mos...
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| Artist impression of Mars ocean |
Excerpt from news.discovery.com
Mars was once a small, wet and blue world, but over the past 4 billion years, Mars dried up and became the red dust bowl we know today.
But how much water did Mars possess? According to research published in the journal Science, the Martian northern hemisphere was likely covered in an ocean, covering a region of the approximate area as Earth’s Atlantic Ocean, plunging, in some places, to 1.6 kilometers (1 mile) deep.
“Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space,” said Geronimo Villanueva, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the new paper, in an ESO news release. “With this work, we can better understand the history of water on Mars.”
Over a 6-year period, Villanueva and his team used the ESO’s Very Large Telescope (in Chile) and instruments at the W. M. Keck Observatory and the NASA Infrared Telescope Facility (both on Mauna Kea in Hawaii) to study the distribution of water molecules in the Martian atmosphere. By building a comprehensive map of water distribution and seasonal changes, they were able to arrive at this startling conclusion.
It is becoming clear that, over the aeons, Mars lost the majority of its atmosphere to space. That also goes for its water. Though large quantities of water were likely frozen below the surface as the atmosphere thinned and cooled, the water contained in an ocean of this size must have gone elsewhere — it must have also been lost to space.
The water in Earth’s oceans contains molecules of H2O, the familiar oxygen atom bound with 2 hydrogen atoms, and, in smaller quantities, the not-so-familiar HDO molecule. HDO is a type of water molecule that contains 1 hydrogen atom, 1 oxygen atom and 1 deuterium atom. The deuterium atom is an isotope of hydrogen; whereas hydrogen consists of 1 proton and an electron, deuterium consists of 1 proton, 1 neutron and 1 electron. Therefore, due to the extra neutron the deuterium contains, HDO molecules are slightly heavier than the regular H2O molecules.
Also known as “semi-heavy water,” HDO is less susceptible to being evaporated away and being lost to space, so logic dictates that if water is boiled (or sublimated) away on Mars, the H2O molecules will be preferentially lost to space whereas a higher proportion of HDO will be left behind.
By using powerful ground-based observatories, the researchers were able to determine the distribution of HDO molecules and the H2O molecules and compare their ratios to liquid water that is found in its natural state.
Of particular interest is Mars’ north and south poles where icecaps containing water and carbon dioxide ice persist to modern times. The water those icecaps contain is thought to document the evolution of water since the red planet’s wet Noachian period (approximately 3.7 billion years ago) to today. It turns out that the water measured in these polar regions is enriched with HDO by a factor of 7 when compared with water in Earth’s oceans. This, according to the study, indicates that Mars has lost a volume of water 6.5 times larger than the water currently contained within the modern-day icecaps.
Therefore, the volume of Mars’ early ocean must have been at least 20 million cubic kilometers, writes the news release.
Taking into account the Martian global terrain, most of the water would have been concentrated around the northern plains, a region dominated by low-lying land. An ancient ocean, with this estimate volume of water, would have covered 19 percent of the Martian globe, a significant area considering the Atlantic Ocean covers 17 percent of the Earth’s surface.
“With Mars losing that much water, the planet was very likely wet for a longer period of time than previously thought, suggesting the planet might have been habitable for longer,” said Michael Mumma, also of NASA’s Goddard Space Flight Center.
This estimate is likely on the low-side as Mars is thought to contain significant quantities of water ice below its surface — a fact that surveys such as this can be useful for pinpointing exactly where the remaining water may be hiding.
Ulli Kaeufl, of the European Southern Observatory and co-author of the paper, added: “I am again overwhelmed by how much power there is in remote sensing on other planets using astronomical telescopes: we found an ancient ocean more than 100 million kilometers away!”
Source: ESO
But how much water did Mars possess? According to research published in the journal Science, the Martian northern hemisphere was likely covered in an ocean, covering a region of the approximate area as Earth’s Atlantic Ocean, plunging, in some places, to 1.6 kilometers (1 mile) deep.
“Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space,” said Geronimo Villanueva, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the new paper, in an ESO news release. “With this work, we can better understand the history of water on Mars.”
Over a 6-year period, Villanueva and his team used the ESO’s Very Large Telescope (in Chile) and instruments at the W. M. Keck Observatory and the NASA Infrared Telescope Facility (both on Mauna Kea in Hawaii) to study the distribution of water molecules in the Martian atmosphere. By building a comprehensive map of water distribution and seasonal changes, they were able to arrive at this startling conclusion.
It is becoming clear that, over the aeons, Mars lost the majority of its atmosphere to space. That also goes for its water. Though large quantities of water were likely frozen below the surface as the atmosphere thinned and cooled, the water contained in an ocean of this size must have gone elsewhere — it must have also been lost to space.
This artist’s impression shows how Mars may have looked about four billion years ago. The young planet Mars would have had enough water to cover its entire surface in a liquid layer about 140 meters deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere.
Also known as “semi-heavy water,” HDO is less susceptible to being evaporated away and being lost to space, so logic dictates that if water is boiled (or sublimated) away on Mars, the H2O molecules will be preferentially lost to space whereas a higher proportion of HDO will be left behind.
By using powerful ground-based observatories, the researchers were able to determine the distribution of HDO molecules and the H2O molecules and compare their ratios to liquid water that is found in its natural state.
Of particular interest is Mars’ north and south poles where icecaps containing water and carbon dioxide ice persist to modern times. The water those icecaps contain is thought to document the evolution of water since the red planet’s wet Noachian period (approximately 3.7 billion years ago) to today. It turns out that the water measured in these polar regions is enriched with HDO by a factor of 7 when compared with water in Earth’s oceans. This, according to the study, indicates that Mars has lost a volume of water 6.5 times larger than the water currently contained within the modern-day icecaps.
Therefore, the volume of Mars’ early ocean must have been at least 20 million cubic kilometers, writes the news release.
Taking into account the Martian global terrain, most of the water would have been concentrated around the northern plains, a region dominated by low-lying land. An ancient ocean, with this estimate volume of water, would have covered 19 percent of the Martian globe, a significant area considering the Atlantic Ocean covers 17 percent of the Earth’s surface.
“With Mars losing that much water, the planet was very likely wet for a longer period of time than previously thought, suggesting the planet might have been habitable for longer,” said Michael Mumma, also of NASA’s Goddard Space Flight Center.
This estimate is likely on the low-side as Mars is thought to contain significant quantities of water ice below its surface — a fact that surveys such as this can be useful for pinpointing exactly where the remaining water may be hiding.
Ulli Kaeufl, of the European Southern Observatory and co-author of the paper, added: “I am again overwhelmed by how much power there is in remote sensing on other planets using astronomical telescopes: we found an ancient ocean more than 100 million kilometers away!”
Source: ESO
Jerdon's BabblerExcerpt from techtimes.comJerdon's Babbler is a species of bird that was believed to be extinct until this species unexpectedly resurfaced in Myanmar. This brown and white bird is roughly the size of a house sparrow.The bird was last ...
Excerpt from nytimes.com
After six years of planetary observations, scientists at NASA say they have found convincing new evidence that ancient Mars had an ocean.
It was probably the size of the Arctic Ocean, larger than previously estimated, the researchers reported on Thursday. The body of water spread across the low-lying plain of the planet’s northern hemisphere for millions of years, they said.
If confirmed, the findings would add significantly to scientists’ understanding of the planet’s history and lend new weight to the view that ancient Mars had everything needed for life to emerge.
“The existence of a northern ocean has been debated for decades, but this is the first time we have such a strong collection of data from around the globe,” said Michael Mumma, principal investigator at NASA’s Goddard Center for Astrobiology and an author of the report, published in the journal Science. “Our results tell us there had to be a northern ocean.”
But other experts said the question was hardly resolved. The ocean remains “a hypothesis,” said Ashwin Vasavada, project scientist of the Curiosity rover mission at the Jet Propulsion Laboratory in Pasadena, Calif.
Dr. Mumma and Geronimo Villanueva, a planetary scientist at NASA, measured two slightly different forms of water in Mars’ atmosphere. One is the familiar H2O, which consists of two hydrogen atoms and one oxygen atom.
The other is a slightly “heavier” version of water, HDO, in which the nucleus of one hydrogen atom contains a neutron. The atom is called deuterium.
The two forms exist in predictable ratios on Earth, and both have been found in meteorites from Mars. A high level of heavier water today would indicate that there was once a lot more of the “lighter” water, somehow lost as the planet changed.
The scientists found eight times as much deuterium in the Martian atmosphere than is found in water on Earth. Dr. Villanueva said the findings “provide a solid estimate of how much water Mars once had by determining how much water was lost to space.”
He said the measurements pointed to an ancient Mars that had enough water to cover the planet to a depth of at least 137 meters, or about 450 feet. Except for assessments based on the size of the northern basin, this is the highest estimate of the amount of water on early Mars that scientists have ever made.
The water on Mars mostly would have pooled in the northern hemisphere, which lies one to three kilometers — 0.6 to 1.8 miles — below the bedrock surface of the south, the scientists said.
At one time, the researchers estimated, a northern ocean would have covered about 19 percent of the Martian surface. In comparison, the Atlantic Ocean covers about 17 percent of Earth’s surface.
The new findings come at a time when the possibility of a northern ocean on Mars has gained renewed attention.
The Curiosity rover measured lighter and heavier water molecules in the Gale Crater, and the data also indicated that Mars once had substantial amounts of water, although not as much as Dr. Mumma and Dr. Villanueva suggest.
“The more water was present — and especially if it was a large body of water that lasted for a longer period of time — the better the chances are for life to emerge and to be sustained,” said Paul Mahaffy, chief of the atmospheric experiments laboratory at the Goddard Space Flight Center.
Just last month, the science team running the Curiosity rover held its first formal discussion about the possibility of such an ocean and what it would have meant for the rest of Mars.
Scientists generally agree that lakes must have existed for millions of years in Gale Crater and elsewhere. But it is not clear how they were sustained and replenished.
“For open lakes to remain relatively stable for millions of years — it’s hard to figure how to do that without an ocean,” Dr. Vasavada said. “Unless there was a large body of water supplying humidity to the planet, the water in an open lake would quickly evaporate and be carried to the polar caps or frozen out.”
Yet climate modelers have had difficulty understanding how Mars could have been warm enough in its early days to keep water from freezing. Greenhouse gases could have made the planet much warmer at some point, but byproducts of those gases have yet to be found on the surface.
James Head, a professor of geological sciences at Brown University, said in an email that the new paper had “profound implications for the total volume of water” on ancient Mars.
But, he added, “climate models have great difficulty in reconstructing an early Mars with temperatures high enough to permit surface melting and liquid water.”
Also missing are clear signs of the topographic and geological features associated with large bodies of water on Earth, such as sea cliffs and shorelines.
Based on low-resolution images sent back by the Viking landers, the geologist Timothy Parker and his colleagues at the NASA Jet Propulsion Lab reported in 1989 the discovery of ancient shorelines. But later high-resolution images undermined their conclusions.
Still, Dr. Parker and his colleagues have kept looking for — and finding, they say — some visible signs of a northern ocean. The new data “certainly encourages me to do more,” he said in an interview.
Other researchers have also been looking for signs of an ancient ocean.
In 2013, Roman DiBiase, then a postdoctoral student at the California Institute of Technology, and Michael Lamb, an assistant professor of geology there, identified what might have been a system of channels on Mars that originated in the southern hemisphere and emptied steeply into the northern basin — perhaps, they said, water flowing through a delta to an ocean.
The background image in this composite shows the Hubble Space Telescope image of the region known as the Hubble Deep Field South. The boxes show distant galaxies that were invisible to Hubble.Excerpt from huffingtonpost.comAlong with Earthrise ...
Excerpt from paranormal.lovetoknow.com By Michelle Radcliff The Bermuda Triangle is an area of mostly open ocean located between Bermuda, Miami, Florida and San Juan, Puerto Rico. The unexplained disappearances of hundreds of ships and air...
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| Venus (right) & Jupiter |
Excerpt from washingtonpost.com
By Blaine Friedlander Jr.
In winter’s waning weeks, Venus and Jupiter continue to accentuate the night heavens, we change our clocks forward and we grab spring with no intention of letting go.
Check the west-southwestern heavens at dusk to spy the vivacious Venus and the dim Mars. In late February, the two planets met for a sweet cosmic waltz, but in March, they appear to separate. Venus approaches negative fourth magnitude (very bright) while Mars makes do at magnitude 1.3 (dim, hard to find in urban light pollution). With a clear sky, Mars looks like a red pinpoint.
A young, waxing crescent moon visits Mars on the evening of March 21, and on the next evening the crescent flirts with Venus.
Robust Jupiter ascends the evening’s eastern sky. Find this gas giant at a -2.5 magnitude, very bright, in the constellation Cancer. The lion in the constellation Leo appears to stare at the planet. By the Ides of March, find it south around 10:30 p.m.
The waxing gibbous moon drops by the dazzling Jupiter on March 2, days before the moon itself becomes full on March 5.
Catch the ringed Saturn rising after midnight in the east-southeast now, hanging out near a gang of constellations, Scorpius, Ophiuchus and Libra. It’s a zero magnitude object, bright enough that it can be seen under urban skies. The waning moon loiters near Saturn before dawn on March 12. On that morning, the reddish star below them is Antares.
We adjust our clocks to Daylight Saving Time at 2 a.m. March 8. Spring forward, moving the clock ahead one hour.
Winter is almost over. Spring is weeks away. The vernal equinox brings spring’s official arrival on March 20 at 6:45 p.m.
Also on March 20 — the day a new moon — the North Atlantic and the Arctic waters get a short total eclipse. We won’t see it here, but Slooh.com will carry it live. Totality will start seconds after 5:44 a.m. and end at 5:47 a.m., according to Geoff Chester of the U.S. Naval Observatory.
Excerpt from nbcnews.com
By Katie Linendoll
FOUNTAIN HILLS, Ariz. — If words like UFO, extraterrestrial, crops circles and abductee have ever piqued your paranormal interest, do yourself a favor and head to the International UFO Congress.
The annual conference—which holds the Guinness record for being the largest convention dedicated to unidentified flying objects—takes place in the picturesque desert town of Fountain Hills, and this year it ran from Feb. 18 to 22. It's worth noting that Arizona is known as a hotbed of activity when it comes to sightings. Thousands flock to the annual event, which is produced by Open Minds, a paranormal research organization.
Each attendee has his or her own reason for being there. My goal was to find out if modern science and technology have changed the game when it comes to UFO sightings and evidence gathering.
"A lot of people think, go to a UFO convention, it's going to be tinfoil hats, but that's not what this is. We have NASA astrobiologists speak, scientists, high-ranking military officials, the works. I mean, there's a lot of really credible people covering this subject," said UFO Congress co-organizer and paranormal journalist Maureen Elsberry.
Air Force UFO documents now available online
When attending a UFO conference, the best approach is to come in with an open mind, ask lots of questions and talk with people about why they are there. Everyone has a story, from the speakers to the attendees, and even the vendors (some of whom double as ufologists).
The highlight of this year's conference was undeniably the speaker series, and it was standing room only to see one man, Bob Lazar. Lazar first spoke out in 1989, claiming that he'd worked as a government scientist at a secret mountainside facility south of Area 51's main site, where he saw remarkably advanced UFO technology. Critics have sought to discredit Lazar, questioning his employment record and educational credentials.
During the conference, George Knapp, an investigative TV reporter in Las Vegas who broke the Lazar story in '89, led an onstage question-and-answer session with Lazar, who discussed the work he did at a place called S4. Lazar spoke in detail about the alien UFO hangars and UFO propulsion systems he was allegedly asked to reverse engineer, and even loosely sketched them out for the audience.
"All the science fiction had become reality," said Lazar, who was noticeably uncomfortable and clearly surprised by the fact that, decades later, he remains such a draw.
You never know whom you'll bump into at the Congress. In the vendor hall, I met sculptor Alan Groves, who traveled all the way from Australia to peddle his "true to scale" Zetan alien figurines. I wondered if his side gig was lucrative, only to realize he was selling the figures like hotcakes. Then we talked about his day job, and he told me he's worked on special and creature effects for films such as "Star Wars," "Alien," "Labyrinth" and "Jurassic Park."
Many of the attendees told me that hard evidence is a requirement for ufologists and paranormal field experts. Derrel Sims, also known as Alien Hunter, told me he spent two years in the CIA, and also has served as a police officer and licensed private investigator.
He said his first alien encounter happened at age 4, and others in his family have also seen aliens. In 38-plus years of alien research, Sims has learned this: "If you look, the evidence is there." To date, he said, more than 4,000 pieces of that evidence exist.
Sims is adamant about only working with evidence-based methods, using DNA tests and collecting samples as well as relying on ultraviolet, infrared and x-ray tools in his research. He said that, in 1992, he discovered aliens leave their own kind of fluorescent fingerprint, and he continues to test for these clues. He added that if you have had an alien encounter, it's important to react quickly to gather evidence: "fluorescence" stays on the skin for only 24 hours. He said that other marks aliens leave include "scoop" marks, which are an identifying thread some abductees have in common.
Another commonality he's discovered is heritage. He said that, in his research, he has found 45 percent of all abductions happen to Native Americans, Irish and Celtic people, and he said that women also have a higher chance of being abducted.
When it comes to filming hard-to-explain phenomena, Patty Greer, who makes documentaries about crop circles, said that quadcopters — a.k.a. drones — have added production value to her films. Lynne Kitei, who covered a mass UFO sighting in her book and in the documentary The Phoenix Lights, said that even low-tech tools, like the 35mm film she used, are still a reliable way to gather proof of inexplicable flying craft, especially because they offer something an iPhone doesn't: negatives.
White House responds to UFO request
Night vision also offers added opportunities for UFO researchers, according to Ben Hansen, who was the host and lead investigator of SyFy channel's "Fact or Faked: Paranormal Files." He's now the owner of Night Vision Ops, an online store that sells night-vision technology. Hansen said that the consumer accessibility of new military-grade technologies in thermal and light amplification scopes are upping the game for the everyday UFO enthusiast.
To close out an intense few days on site at the Congress, Hansen's team invited me to a night watch near Arizona's Superstition Mountains. It was fascinating to see the latest optics add incredible clarity to the night sky, amplifying available light up to 50,000 times beyond what the unaided eye can see. Using the right technology, we were also able to see that a certain flying object, which made everyone nearby jump, wasn't a UFO after all. It was a bat.
I was surrounded by some serious tech all weekend, and it was eye-opening to see the ways that UFO hunters are gathering scientific evidence to learn more about the paranormal world. But I have to say, the gadget that was the most useful to me at the conference was my iPhone, which I used to download a free nightlight app for kids. For the few hours I managed to sleep, it was with the soothing illumination provided by "Kiwi the Green Koala." In short, I was officially freaked out.
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| The oldest samples are sedimentary rocks that formed 3.2 billion years ago in northwestern Australia. They contain chemical evidence for nitrogen fixation by microbes.R. Buick / UW |
Excerpt from
washington.edu
A spark from a lightning bolt, interstellar dust, or a subsea volcano could have triggered the very first life on Earth.
But what happened next? Life can exist without oxygen, but without plentiful nitrogen to build genes – essential to viruses, bacteria and all other organisms – life on the early Earth would have been scarce.
The ability to use atmospheric nitrogen to support more widespread life was thought to have appeared roughly 2 billion years ago. Now research from the University of Washington looking at some of the planet’s oldest rocks finds evidence that 3.2 billion years ago, life was already pulling nitrogen out of the air and converting it into a form that could support larger communities.
“People always had the idea that the really ancient biosphere was just tenuously clinging on to this inhospitable planet, and it wasn’t until the emergence of nitrogen fixation that suddenly the biosphere become large and robust and diverse,” said co-author Roger Buick, a UW professor of Earth and space sciences. “Our work shows that there was no nitrogen crisis on the early Earth, and therefore it could have supported a fairly large and diverse biosphere.”
The results were published Feb. 16 in Nature.
The authors analyzed 52 samples ranging in age from 2.75 to 3.2 billion years old, collected in South Africa and northwestern Australia. These are some of the oldest and best-preserved rocks on the planet. The rocks were formed from sediment deposited on continental margins, so are free of chemical irregularities that would occur near a subsea volcano. They also formed before the atmosphere gained oxygen, roughly 2.3 to 2.4 billion years ago, and so preserve chemical clues that have disappeared in modern rocks.
Even the oldest samples, 3.2 billion years old – three-quarters of the way back to the birth of the planet – showed chemical evidence that life was pulling nitrogen out of the air. The ratio of heavier to lighter nitrogen atoms fits the pattern of nitrogen-fixing enzymes contained in single-celled organisms, and does not match any chemical reactions that occur in the absence of life.
“Imagining that this really complicated process is so old, and has operated in the same way for 3.2 billion years, I think is fascinating,” said lead author Eva Stüeken, who did the work as part of her UW doctoral research. “It suggests that these really complicated enzymes apparently formed really early, so maybe it’s not so difficult for these enzymes to evolve.”
Genetic analysis of nitrogen-fixing enzymes have placed their origin at between 1.5 and 2.2 billion years ago.
“This is hard evidence that pushes it back a further billion years,” Buick said.
Fixing nitrogen means breaking a tenacious triple bond that holds nitrogen atoms in pairs in the atmosphere and joining a single nitrogen to a molecule that is easier for living things to use. The chemical signature of the rocks suggests that nitrogen was being broken by an enzyme based on molybdenum, the most common of the three types of nitrogen-fixing enzymes that exist now.
Molybdenum is now abundant because oxygen reacts with rocks to wash it into the ocean, but its source on the ancient Earth – before the atmosphere contained oxygen to weather rocks – is more mysterious.
The authors hypothesize that this may be further evidence that some early life may have existed in single-celled layers on land, exhaling small amounts of oxygen that reacted with the rock to release molybdenum to the water.
“We’ll never find any direct evidence of land scum one cell thick, but this might be giving us indirect evidence that the land was inhabited,” Buick said. “Microbes could have crawled out of the ocean and lived in a slime layer on the rocks on land, even before 3.2 billion years ago.”
Future work will look at what else could have limited the growth of life on the early Earth. Stüeken has begun a UW postdoctoral position funded by NASA to look at trace metals such as zinc, copper and cobalt to see if one of them controlled the growth of ancient life.
Other co-authors are Bradley Guy at the University of Johannesburg in South Africa, who provided some samples from gold mines, and UW graduate student Matthew Koehler. The research was funded by NASA, the UW’s Virtual Planetary Laboratory, the Geological Society of America and the Agouron Institute.
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